In many conventional printers, individual sheets of paper or other print media are fed into the printer off the top of a stack of sheets held in a horizontally oriented tray. Typically, a pick roller is rotated against the top sheet to slide the top sheet off the stack and into the printer. Friction between sheets in the stack sometimes causes the top two or three sheets in the stack to stick together as the top sheet is picked from the stack. The next-to-top sheets must be separated from the top sheet to avoid feeding multiple sheets into the printer at the same time. In one conventional input structure for a horizontal feed printer, the next-to-top sheets are separated from the top sheet by driving the sheets across an elastomeric pad positioned at the front of the media input tray. This pad is often referred to as a separator pad because it's function is to separate the top sheet in the stack from next-to-top sheets in the stack so that only the top sheet moves into the printer. In some printers, such as Hewlett-Packard Company's Deskjet® 5150 model injet printer, the separator pad is lifted against the pick roller at the beginning of the pick cycle and then quickly lowered to momentarily increase the separating effect of the pad.
The active separator pad design used in the Deskjet® 5150 works well when media sheets are picked from a horizontal stack, where the separator pad need overcome only the friction force between sheets. If this active separator pad design is used when sheets are picked from a vertically oriented stack, however, gravity can pull multiple sheets into the media path as soon as the pad is moved away from the pick roller, resulting in more than one sheet being fed into the printer.